Process of bending tubes.



bPAV'I'ENTED APBn 19, 1904- y. No. 757,592.

- F. ATWooD.

PROCESS 0F BBNDING TUBES.

APPLIOATION FILED JULY 11, 1902.'.

2 SHEETS-SHEET 1,

N0 MODEL.

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a Y 1 Way PATENTED APR. 19, 1904.

G. SQA'TW'UOD. PROCESS 0F BBNDNG TUBES.

APPLICATION FILED JULY 1l, 1902.

2 SHEETS-SHEBT 2.

ND MODEL.

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,Notre-Z592.

Nrrsn STATES segr avenants com Patented April 19, 1904.

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GEORGE Ff ATIVOOD, OF HOBOKE, NEW JERSEY, ASSIGN-OR TO WEST- EBNELECTRIC. COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF .ncLnyolsPFioor-:Ss oF BENDlNe TUBES.

` srEcIFleA'rIoN forming part of Letters Patent No. 757,592, dated April19, 1904.

Application filed July 11,1902. serial No. 115,107. (No specimens.)

To all whom t may concern.:

Beit known that I, GEORGE F. A'rwool), a

citizen of the United States, residing at Hobeken, in the lcounty ofHudson and State of N ew Jersey, have invented a. certain new and usefulImprovement in Machines forBending Tubes, of which the following is afull, clear, concise, and exact description.

My invention relates to a process for bending tubes, and isuseful moreparticularly in bending tubing of rectangular cross-'section'- such, forinstance, as that used in a wellknown pneumatic'tube system fordistributing toll-tickets in telephone-exchanges.

The problem of bending a rectangular tube presents much greaterdiiculties than the bending of round tubes, and it has been found' thatthe methods heretofore employed for the latter will not attain thedesired results with rectangular tubing. It is frequently required tobend the rectangular tube on a radius of three or four inches withoutdistortion .or wrinkles, and in such a case the outer wall and` the twoedges must stretch a very considerable distance more than theinner wall.In attem ptin g to bend a thin rectangular tube by the methodsheretofore employed it is found that before vthe outer wall will-stretchthe required amount the inner wall will be buckled and distorted. Thelilling of sand ordinarily used may prevent the metal from bucklinginward; but it will then buckle outward, which no filling willeflectually prevent.

A ln accordance with my invention the tube is iirst subjected toalongitudinal tensile stress sutiicient to stretch the metal, and thenthe tube is bent while such tensile strain is maintained. 'Prefer-abi ythe tube is stretched to approximately the elastic limit of the metal,and this stress is gradually increased as the tube is bent. I have foundthat by this process a perfectly regular and symmetrical curve or twistwithout the slightest distortion or wrinkle can be produced.

A machine for practicing the process in question is shown in theaccompanying drawings, in connection with which 1 will moreparticularlydescribe my invention. The machine 1s made thesubject-matter of another' application for patent, Serial No. 115, 108,filed July '11, 1902. l

Figure 1 is a view'of the machine in elevation. Fig. 2 is a sectionalplan View thereof on line Q 2 of Fig.' 1. Fig. 3 is an end elevation.Fig. 4 is a sectional plan view similar to Fig. 2, but showing the partsin an alternative position. ing how the tube may be given a twist orquarter-turn. Figs. 6 and 7 are detail views showing. how the tube isplugged at the points where it is clamped,`,so tllat it will notcollapse.

The same letters of reference designate the same parts Whereverthey'areshown.

The rigid framework a', which may be supported on legs or standards hasa threaded bearing c at one end, through which the longitudinal screw cis passed. The .inner end of said screw carries a liead or cin'ck d,which is mounted thereon so that the screw can rotate independentlythereof. A removable cross-bar t' is fitted upon pins carried by thechuck (Z and projects above and below the same alongside the horizontalbars of the `framework, so that when said cross-bar is in place thechuck cannot rotate, but will merely slide forward or backward as thescrew is turned; iVhen thc cross-bar is removed, the chuck may berotated by the aid of a wrenchbar-thrust into one of theholesflj3 in itsperiphery- At the other end of the framework mis mounted a verticalshaft e', which carries the bending mandrel f, the shaft being sodisposed that the curve of the mandrel will be approximately tangent ltoa line projected along the longitudinal axis of the screw.

'lhe head or chuck (Z is provided with jaws ai f, which are adapted tograsp one end of the tl'lbing, said jaws being tightened by means ofbolts di d2. Clamps g (7, tightened by bolts g1 y, are placed upon theother end of the tubing, and these clamps are seated against lugsf' f',which project from the top and bottom of the bending-mandrel. Plugs t /Lare inserted in the tube at the points where it is clamped topreventcollapse. The tubo is also lilled with sand or other filling inaccordance with tlle'usual practice.

'.lhc screw c has-a' long keyway c', along Fig. 5 is a detail view showysupported upon the lugsy" f of the bendingperiphery of the mandrel willmove slightly which a pinion c2 is adapted to slide, said pinm ion beingthus thrown into or out of mesh with a spur-gear le, as may be desired.The spur-gear'o is fixed upon one end of the shaft le', the other endwhereof carries a worm k2, which engages a worm-wheel r, fixed upon theVertical shaite' of the lbending-mandrel.

The operation of the machine is as follows: A tube of suitable length isplugged and filled with sand and one end clamped between the jaws d d ofthechuck d, while the 4clamps g g, whichare placed on the other end, are

mandrel, as shown in Figs. 1 vand The pinion c2 is now removed from meshwith the spur-gear it', and the screw c is turned backward by a crank or-other means to put a longitudinal tensile stress on the tube, themandrel f being held immovable by the worm-gear and the h e'ad or chuckOZ being retracted by the screw. When this stress-is suiiicient toelongate the tube', the pinion c2 is thrown into mesh with the spur-gears, and the screw c is then turned forward. Now as the screw is rotatedthe pinion c drives the bending-mandrel f through the gearing beforedescribed; which is preferably so proportioned that the faster than thechuck d, whichis advanced by the screw. By this means not only theinitial x stress on the tube is Ikept up, but the stress i is graduallyincreased as the bend is made. l Fig. 4 shows the position of themandrel in l finishing a bend of ninety degrees. The stress upon thetube is so ygreat that the inner wall can not buckle while the'outerwall is stretched, and a perfectly regular and smooth bend is thussecured.

Wrhen desired, the tubes may be given a twist, as shown in Fig. 5. Thismay be done by removing the cross-bar t' from the chuck.

d, so leaving the latter free to turn, and then rotating saidchuckthrough the required are by means of a wrench-bar thrust into one of'the holes d.

i claim as my inventionl. The herein-described process of bending metaltubes which consists in first subjecting the tube to a longitudinaltensile stress sutiicient to stretch the tube approximately to theelastic limit of the instal, and then bending the tube while maintainingsuch a tensile stress.

2. The herein-described process of bending metal tubes which consists insubjectingthc vtube to a longitudinal tensile stress suiicient

